Conversion of Nitroalkenes into β-(Trichloromethyl) Nitroalkanes

The cesium fluoride-catalyzed reaction of (trichloromethyl) - trimethylsilane with conjugated nitroalkenes affords β-(trichloromethyl)nitroalkanes.     

New Synthesis of (±)-Cherylline and Mono- and Dimethyl Ethers

The synthesis of 4-aryl-1,2,3,4-tetrahydroisoquinolines is achieved via the ether rearrangement methodology. Subsequent reactions yielded cherylline and ether derivatives of amaryllidaceac alkaloids.     

Selected Reaction of (Z)-Dimethyl α-(Bromomethyl) Fumarate with Secondary Amines

Regioselective reaction of (Z)-dimethyl α-(bromomethyl) fumarate 2 with bulky secondary amines in ether as solvent at room temperature, leads exclusively to the rearranged substitution α-(functional alkyl amino) acrylic esters 4a-i in high yields. The less and more bulky amine gives rise respectively to the two successive (S_N2′) and (S_N2) substitution derivatives 5j,k and 51.     

Diastereoselective Allylation of α-Hydroxy Schiff Bases with 2-Substituted Functionalized Allyl Bromides

Russian Journal of Organic Chemistry - The allylation of α-hydroxy Schiff bases with 2-substituted functionalized allyl bromides such as methyl 3-(bromomethyl)but-3-enoate,...     

Oxidative Transformation of Functionalized Methyl Ketones into α-Ketocarboxylic Esters

Methyl ketones are oxidatively transformed into α-keto esters by metal ion assisted alcoholysis of the corresponding β-keto-α, α-dichloroalkyl sulfides.     

Dehydrogenative α-Oxygenation of Cyclic Ethers by a High-Valent Manganese(IV)-Oxo Species

High-valent metal-oxo species are typical catalytic cycle intermediates in mono-oxygenases and dioxygenases and commonly react through oxygen atom transfer to substrates. In this work we study a biomimetic model complex with a 1,1’-bis((3,5-dimethylpyridin-2-yl)methyl)-2,2’-bipiperidine ligand system bound to a manganese(IV)-oxo(hydroxo) species and study its formation from manganese(II)-hydroxo and H₂O₂ as well as its reaction with (S)-1-phenylisochromane through dehydrogenative α-oxygenation. The work utilizes density functional theory methods to explore its catalytic cycle and its reactivity patterns. We show that the manganese(IV)-oxo(hydroxo) species is an active oxidant and preferentially the oxo group abstracts a hydrogen atom from substrate with barriers well lower in energy than those found for hydrogen atom abstraction by the hydroxo group. Interestingly, the rate-determining step is the OH rebound rather than the hydrogen atom abstraction, which would imply they would have limited kinetic isotope effect for the replacement of the transferring hydrogen atom by deuterium.     

Stereoelective Conversion of Ethyl Pipecolinate into (±)-α- and (±)-β-Conhydrins

Reaction of ethyl N-benzhydrylpipecolinate with ethylmagnesium bromide in the presence of catalytic amount of titanium(IV) isopropoxide furnished in a high yield the corresponding hydroxypropyl-substituted piperidine that by treating with alcoholic alkali was quantitatively converted into 1-benzhydryl-2-propionylpiperidine. The reduction in the latter of carbonyl group with lithium aluminum hydride or sodium borohydride in methanol gave rise prevailingly to threo-aminoalcohol. With sodium borohydride in the presence of cerium chloride an erythro-aminoalcohol was the main product. Deprotection of the nitrogen atom from the benzhydryl group of the aminoalcohols obtained provided racemic - and -conhydrines.     

The silapinacol rearrangement: Conversion of α,β-dihydroxysilanes into α-silyl carbonyl compounds

Treatment of α,β-dihydroxysilanes with trifluoroacetic acid in chloroform results in a 1,2-migration of the silyl group to give α-silyl aldehydes and ketones. The t-butyldimethylsilyl compounds can be isolated in high yields.     

Catalytic Enantioselective Synthesis of Functionalized Cyclopropanes from α-Substituted Allyl Sulfones with Donor-Acceptor or Diacceptor Diazo Reagents

The catalytic asymmetric synthesis of highly functionalized cyclopropanes from α-substituted allyl sulfones and silanes is reported. The reaction, using α-aryl diazoacetates or diacceptor diazo reagents, catalyzed by a chiral rhodium complex (Rh₂((S)-BTPCP)₄), furnished the corresponding cyclopropanes in moderate to high yields (27–97 %), high diastereoselectivities (68 : 32 to 20 : 1 d.r.) and moderate to excellent ee (40–99 %). This methodology offers a privileged access to an underexplored class of enantioenriched cyclopropanes with a high level of functionality, an asset for further post-functionalization and their incorporation into more complex structure.     

Protected β-Dicarbonyl Compounds: Alkylation of Trimethyl Silyl Enol Ethers with Tris-(Phenylseleno) Methane Mediated by Tin Tetrachloride

β,β-Bis-(phenylseleno) carbonyl compounds were prepared by reacting the corresponding silyl enol ether with tris-(phenylseleno) methane in the presence of tin tetrachloride.     

Conversion of isoxazole derivatives into β-aminoenones by pentacarbonyliron,water and photoirradiation

3,5-Disubstituted isoxazole derivatives, when irradiated in the presence of pentacarbonyliron and water undergo reductive cleavage of the NO bond to give β-aminoenones in good yields.     

Transition-Metal-Free Borylation of Aryltriazene Mediated by BF(3)·OEt(2)

A practical and simple method for deaminoborylation of aryltriazene with bis(pinacolato)diboron has been developed that is mediated by BF(3)·OEt(2). Various arylboronic esters are prepared in moderate to good yields with this facile transition-metal-free procedure.     

New Acyclic β-Functionnalized (E) Allyl Alcohols and their Bromomethyldimethylsilyl Ethers as Cyclopentanoids Precursors

The syntheses of new acyclic (E) allyl alcohols β-functionnalized by various radical trapping functions and their corresponding bromomethyl-dimethylsilyl ethers are reported.     

Conversion of Alkynes into α,α-Dichloro Ketones and α,α-Dichlorodimethyl Ketals Using Trichloroisocyanuric Acid

Abstract

Trichloroisocyanuric acid reacts with alkynes in the presence of water in acetone or acetonitrile to form α,α-dichloro ketones and in methanol to form α,α-dichlorodimethyl ketals.     

Synthesis of α,β-Unsaturated Nitriles by Reaction of Haloacetonitrile with Carbonyl Compounds Mediated by Tri-n-butylstibine

α,β-Unsaturated nitriles were synthesized by the reaction of haloacetonitriles with carbonyl compounds mediated by tri-n-butylstibine in excellent yields.     

Fluorinated α-Diimine Nickel Mediated Ethylene (Co)Polymerization

Fluorine substituents in transition metal catalysts are of great importance in olefin polymerization catalysis; however, the comprehensive effect of fluorine substituents is elusive in seminal late transition metal α-diimine catalytic system. In this contribution, fluorine substituents at various positions (ortho-, meta-, and para-F) and with different numbers (F_n; n=0, 1, 2, 3, 5) were installed into the well-defined N-terphenyl amine and thus were studied for the first time in the nickel α-diimine promoted ethylene polymerization and copolymerization with polar monomers. The position of the fluorine substituent was particularly crucial in these polymerization reactions in terms of catalytic activity, polymer molecular weight, branching density, and incorporation of polar monomer, and thus a picture on the fluorine effect was given. As a notable result, the ortho-F substituted α-diimine nickel catalyst produced highly linear polyethylenes with an extremely high molecular weight (M_w=8703 kDa) and a significantly low degree of branching of 1.4/1000 C; however, the meta-F and/or para-F substituted α-diimine nickel catalysts generated highly branched (up to 80.2/1000 C) polyethylenes with significantly low molecular weights (M_w=20-50 kDa).     

One-Pot Approach to the Conversion of Alcohols into α-Iodo-α,β-unsaturated Esters

(Carboethoxymethylene)triphenylphosphorane 1 can undergo the tandem reaction of iodination–oxidation–Wittig reaction with alcohol in the presence of N-iodosuccinimide (NIS) and manganese dioxide. The reaction constitutes a stereoselective one-pot procedure for the preparation of Z-configured α-iodo-α,β-unsaturated esters in good to excellent yield.     

Synthesis of α-(perfluoroalkyl)-ω-(trialkylsilyl)alkanols

The synthesis of alkanols of the general formula R₃Si(CH₂)_nCH(OH)R_F (n = 1–3) is elaborated and their behavior under GC-MS is studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1516-1519, June, 1996.     

Theoretical investigations into the enantiomeric and racemic forms of α-(trifluoromethyl)lactic acid

There are many different hypotheses on the origin of biomolecular homochirality. One possible scenario concerns the enantiomeric enrichment of a nearly racemic solid via self-disproportionation of enantiomers. In particular, in a recent paper Soloshonok and co-workers showed a first example of optical self-purification of α-(trifluoromethyl)lactic acid by sublimation [V. A. Soloshonok et al., J. Am. Chem. Soc. 2007, 129, 12112]. Here we present detailed theoretical studies of α-(trifluoromethyl)lactic acid in the solid state as well as in the gas-phase dimeric form. The calculations of energy differences between dimers show that in the solid state the enantiomeric pure compound is energetically preferred, while in the gas phase the equilibrium shifts towards the racemic mixture although thermodynamic corrections cannot be neglected, thus providing a detailed microscopic explanation for the enantio-purification process for the first time.